Process for making positive diazotype copies by exposure to light of a mercury vaporlamp and light-sensitive material suited for this process



United States Patent 3,081,166 PROCESS FOR MAKING POSITIVE DIAZOTYPE COPIES BY EXPOSURE TO LIGHT OF A MER- CURY VAPOR LAMP AND LIGHT-SENSITIVE MATERIAL SUITED FOR THIS PROCESS Arie van Loon and Karel Maria Hutgens, Venlo, Netherlands, assignors to Chemisch'e Fabriek L. van der GrintenN.V., Venlo, Netherlands, a corporation of the v Netherlands No Drawing. Filed Feb. 4, 1958, Ser. No. 713,105

Claims priority, application Netherlands Feb. 5, 1957 2 Claims. (Cl. 96-27) The invention relates to a proce s s for making positive diazotype copies and to light-sensitive diazotype material suited for carrying out this process.

For some years past actinically fluorescent mercury vapour lamps have been employed in exposure apparatus for heliographic printing purposes. The fluorescent substance with which these lamps are coated, mostly on the inside, improves their emission spectrum for the purposes mentioned and generally also for the positive diazotype process. The latter is carried out according to the onecomponent process by development with an azo-coupling component solution or according to the two-component process with diazo compound and azo-coupling component together in the light-sensitive layer and development with alkali.

In making copies the determination of the endpoint of the exposure is of importance. In practice this is sometimes done in the positive diazotype process by means of visual observation. The visual determination is uncertain in the case of exposure with non-fluorescent lamps; upon exposure of the usual diazotype materials with actinically fluorescent lamps the observed endpoint lies too far before the point at which the diazotype material has received the exposure desired in practice. This being so, in practice the exposure is continued at random for a short time, but this naturally involves errors. Such a process is necessary when p-diazodiphenyl-amine, a diazo compound which is known to be particularly suited for visual endpoint determination, is employed.

According to the present invention an actinically fluorescent mercury vapour lamp is used as light-source for the image-wise exposure, while for copying use is made of a diazotype material the light-sensitive layer of which contains a diazo compound of the general formula:

in 'which X represents an anion, R represents an alkyl group with at most 4 carbon atoms, R represents an alkyl group with at most 4 carbon atoms oran aralkyl group with at most-7 carbon atoms, and R represents an alkyl group with at most 4 carbon atoms.

In using this combination of material and lamp the visually observable endpoint of the exposure lies particularly near to the point at which the diazotype material TL/5 type lamp of N.V. Philips Gloeila-mpenfabriek,

Eindhoven, Holland, which emits light that the human eye observes as white to blue light Although this light .to the above description.

M CC

contains a variety of wavelengths, including emissions in a continuous spectrum in the range between about 3000 and 4700 Angstrom uni-ts with the maximum emission at about 3655 Angstrom units and certain emissions in the green-yellow range above 5000 Angstrom units, its prevailing wavelengths perceptible to the human eye lie in the blue range between 4000 and 4700 Angstrom units.

The diazo compounds in which the substituents R R and/or R contain 3 or 4 carbon atoms are better suited for the one-component diazotype process while those in which these substituents are methyl and/or ethyl groups are to be preferred for the two-component diazotype process. If R is an aralkyl group or if, in the absence of an aralkyl group, one of the substituents R R or R is an alkyl group of 3 or 4 carbon atoms, the compound is already suited for the one-component diazotype process. Consequently, the number of compounds suited for the one-component process is relatively large. With the compounds suited for the one-component process suitable two-component di-azotype materials may also be obtained. In that case azo components of poor coupling activity and/ or coupling-retarding agents are preferably employed in the material. If one or more of the substituents are alkyl groups with three or four carbon atoms (for example, normal butyl or isobutyl), it should be taken into account that the diazo compounds may have a capillary-active eifect. In aqueous solution these compounds penetrate deeply into the usual base-papers upon sensitization. The visual determination of the endpoint of the exposure is thus made diflicult and the light-sensitivity of the diazotype material, as well as the strength of the copies, decreases. Such diazo compounds are, however, better suited for sensitizing film layers, for example, superficially saponified cellulose-ester layers, and natural tracing paper.

The light-sensitive material for the new process may of course contain mixtures of diazo compounds according Mixtures with other diazo compounds may also be suitable. In that case, however, the eflect is smaller.

Diazotype material which is particularly suited for carrying out the process according to the invention contains as the light-sensitive compound a diazo compound of the type of 1-diazo4-(alkyl) (benzyl)amino-3-alkoxybenzene, the two alkyl groups of which contain together at most 3 carbon atoms. 1

These diazo compounds have various attractive properties: they are suificiently soluble, their solutions do not penetrate deeply into the paper; they keep well; they are able to form black azo-clyestufis upon development of diazotype material sensitized therewith. The diazo compounds with a benzyl group, for use in the process according to the invention, give entirely colourless photochemical decomposition products upon exposure.

Diazotype material particularly suited for the process contains, as the light-sensitive compound, 1-diazo-4-din-propylamino-3-ethoxybenzene; the compound is readily available.

The azoalyestuif images obtained by development of these materials with a diazotype developer containing phloro-glucinol are more resistant to change of pH; in

other words,'they keep their colour at relatively greater copies obtained according to the process often also have good absorption and great contrast for rays in the near ultra-violet. In consequence, intermediate copies made according to the new process are particularly suitable for recopying. They have good resistance to the ultra-violet light to which they are exposed upon recopying.

The diazo compounds according to the invention are readily available. For the compounds with a methoxy or an ethoxy group the starting material is o-anisidine or o-phenetidine; for the compounds with other alkoxy groups it is o-nitrophenol, which is alkylated and subsequently reduced. In the o-aminophenylalkylether the amino group is then alkylated. The resulting o-alkoxydialkylaniline is thereupon nitrosated in acetic acid, the nitroso compound is reduced, for example with hydrochloric acid and aluminium powder, and the p-amino compound is diazotized.

Instead of being nitrosated, the o-olkoxy-dialkylaniliue may be caused to couple with an actively coupling diazo compound, for example, 1 diazo 2.5 dichlorobenzene. The azo-dyestulf obtained is reduced, the 2.5-dichloroaniline thus formed is separated from the p.amino-oalkoxy-dialkylaniline formed at the same time, and the latter is diazotized.

The diazo compound is obtained from the diazotizing liquid by precipitation in the form of diazonium salt, for example a diazonium borofluoride or a diazonium zinc chloride double salt. With regard to the above-mentioned alkylation of the amino group it should be noted that: R and R may be the same or different alkyl groups. Their carbon chain may or may not be branched, provided their presence in the molecule of the diazo compound in the places indicated is possible from the point of view of structure of the molecule.

The following examples will serve to illustrate the invention.

Example 1 White base-paper of 80 g./m. for the diazotype process is sensitized with a solution of:

22 g. of zinc chloride double salt of 1-diazo-4-(methyl) (benzyl amino-S-ethoxybenzene,

7 g. of tartaric acid and 0.8 g. of methylcellulose in 1000 cc. of water and dried.

The sensitized surface contains approximately 0.5 millimole of the diazo compound per m A sheet of the diazotype paper is exposed under a film positive of a pencil line-drawing on the outer surface of a glass cylinder in the axis of which is placed an actinically fluorescent low-pressure mercury vapour lamp of the TL/ type, of N. V. Philips Gloeilampenfabriek, Eindhoven. The sheet of diazotype paper, together with the line-positive, is held against the cylinder surface by means of an apron. The distance from the outer surface of the cylinder to the centre of the lamp is 9.5 cm. The progress of the bleaching of the yellow diazo compound in the diazotype surface can easily be observed visually, for example, from the direction of the lamp; the endpoint of the observation is reached after approximately 55 seconds. The exposure is stopped at this point.

The latent diazotype copy obtained is developed by applying on its image surface a layer of approximately 8 g./n1. of the following developer:

250 g. of sodium formate 10 g. of phloroglucinol 3 g. of 2-ethyl-hexyl-sulphuric acid as sodium salt 1000 cc. of water The developed copy shows a strong black positive image on a weakly fogged background, which background entirely meets the practical requirements. When the copying is repeated, an observer with normal eyesight will each time obtain a copy with the same weakly fogged background. It is to be noted that it is a practical requirement that diazotype copies of pencil tracings or of the transparent film positives corresponding therewith should have a Weakly fogged background; furthermore it is remarked that most of the originals to be copied in practice are of this kind. If the process had been carried out with p-diazo-diphenylamine in a way entirely corresponding to that described above, the developed copy would have shown a background so strongly fogged that it would not have fulfilled the practical requirements.

If the exposure had been carried out in the light of a non-fluorescent mercury vapour lamp, no sharp endpoint would have been observed, and upon repetition in most cases an overexposed, faint copy would have been obtained.

Example II Natural tracing paper of g./m. is sensitized with a solution of:

40 g. of zinc chloride double salt of 1-diaZo-4-n-propylamino-3-n-propoxy benzene,

10 g. of tartaric acid in 300 cc. of ethanol and 700 cc.

of water 31 g. of thiourea 6.5 g. of phloroglucinol 6.5 g. of resorcinol 2 g. of isopropylnaphthalene sulphonic acid as sodium salt 5 g. of eorbitol 15 g. of beet sugar 53 g. of potassium tetraborate (5 aq.)

9 g. of potassium hydroxide in 1000 cc. of water The intermediate copy obtained is excellently legible, shows the fog most desirable in practice, and upon further copying yields strong copies on diazotype paper.

Example 111 White base-paper of 80 g./m.

is sensitized with a solution of:

salt of l-diazo-4-diethylfor the diazotype process 20 g. of zinc chloride double amino-3-ethoxybenzene 40 g. of citric acid 10 g. of thiourea 20 g. of 7'-hydroxy-l.2.4.5-naphthoimidazole 30 cc. of polyvinylacetate dispersion (Vinnapas H. 60 of Wacker-Chemie G.m.b.H., Germany) in 1000 cc. of water and dried.

The sensitized surface contains approximately 0.5 millimole of the diazo compound per m A sheet of the diazotype material is exposed as in Example I. The latent diazotype copyobtained is developed in ammonia vapour.

The developed copy shows a strong red azo-dyestuff image with the fog most desirable in practice.

What we claim is:

l. A process for making diazotype copies, which comprises imagewise exposing to the light of an actinically fluorescent mercury vapor lamp a diazotype sheet material having a light-sensitive layer containing a 1-diazo-4- alkylbenzyl amino-B-alkoxy-benzene in which the alkyl groups together contain from 2 to 3 carbon atoms, said lamp being one having emissions in a continuous spectrum in the range between about 3000 and 4700 A. with the maximum emission at about 3655 A. and having certain emissions in the range above 5000 A. and its prevailing wavelengths perceptible to the human eye being in the range between 4000 and 4700 A.

2. A diazotype material comprising a sheet-like support carrying a light-sensitive layer containing as its principal light-sensitive constituent a 1-diazo-4-alkylbenzy1 amino- 3-a1koxybenzene in which the alkyl groups together contain from 2 to 3 carbon atoms, said layer upon being exposed to the light of an actinically fluorescent meroury vapor lamp attaining a stage of optimum exposure when a portion of said layer being exposed to said light appears to the human eye to :have become bleached by the exposure, said lamp being one having emissions in a continuous spectrum in the range between about 3000 and 4700 A. with the maximum emission at about 3655 A. and having certain emissions in the range above 5000 A. and its prevailing Wavelengths perceptible to the human eye being in the range between 4000 and 4700 A.

6 References Cited in the file of this patent UNITED STATES PATENTS 2,532,744 Straley Dec. 5, 1950 2,606,117 Trojnar Aug. 5, 1952 FOREIGN PATENTS 629,656 Great Britain Sept. 26, 1949 650,046 Great Britain Feb. 14, 1951 997,706 France Sept. 12, 1951 OTHER REFERENCES Fluorescent Lighting, edited by C. Zwikker, Phillips Technical Library, Eindhoven, Netherlands, 1952, pages 92, 93.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 O8l l66 March 12 1963 Arie van Loon etv a1,

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 4 line 16 for "1-d1 m W read 1H diazo -4-di-n m. M,

Signed and sealed this 1st day of October 1963.

(SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attcsting Officer Commissioner of Patents 

1. A PROCESS FOR MAKING DIAZOTYPE COPIES, WHICH COMPRISES IMAGEWISE EXPOSING TO THE LIGHT OF AN ACTINICALLY FLOURESCENT MERCURY VAPOR LAMP A DIAZOTYPE SHEET MATERIAL HAVING A LIGHT-SENSITIVE LAYER CONTAINING A 1-DIAZO-4ALKYLBENZYL AMINO-3-ALKOXY-BENZENE IN WHICH THE ALKYL GROUPS TOGETHER CONTAIN FROM 2 TO 3 CARBON ATOMS, SAID LAMP BEING ONE HAVING EMMISSIONS IN A CONTINOUS SPECTRUM IN THE RANGE BETWEEN ABOUT 3000 AND 4700 A. WITH THE MAXIMUM EMISSION AT ABOUT 3655 A. AND HAVING CERTAIN EMISSIONS IN THE RANGE ABOVE 5000 A. AND ITS PREVAILING WAVELENGTHS PERCEPTIBLE TO THE HUMAN EYE BEING IN THE RANGE BETWEEN 4000 AND 4700 A. 